Inherited attributes from a referenced 'pattern' are not applied if they are already defined on the referencing 'pattern' element.
Define a pattern 'pattern1' with circles that have red fill. Inherit 'pattern1' into 'pattern2' and add circles at different 'y' attribute and with 'fill' set to 'lime' on 'pattern2'. Reference 'pattern1' from a square using 'fill' attribute. Reference 'pattern2' from a different square using 'fill' attribute. Position the second square directly over the first square. Verify that there is green visible.
Run the test. No interaction required.
The test is passed if there are four green circles visible on the page, and no red.